Surely I can't be the only one who thinks she was just making a funny face, as young children tend to do often? When I was around that age, I had a tendency to puff my cheeks when being photographed c:

83, a pop in the mouth is definitely not abuse. Especially when deserved. My mom never hit me, but when I back talked I got popped on my mouth. And I learned.
I would hope if I was 6 and made a stupid ass duck face for a school picture that she'd be pissed. The younger generation worries me.